The Centers for Medicare and Medicaid Services announced Thursday it has posted new ratings on 4,000 hospitals on its "Hospital Compare" Web site, including new mortality and readmission data.

According to the new data, CMS estimates that the national 30-day mortality rate for patients originally admitted for heart attack care is 16.6 percent. For heart failure patients, the national 30-day mortality rate is 11.1 percent, and for pneumonia patients the national rate is 11.5 percent.

CMS officials said readmission data - how frequently patients return to a hospital after being discharged - may be "a possible indicator of how well the facility did the first time around."

CMS officials said the agency has also updated its Hospital Compare Web site with better data on the previously posted mortality rates for individual hospitals, as well as new data on 30-day readmissions for heart attack, heart failure, and pneumonia. Previously, Hospital Compare had provided only mortality rates for these three conditions. The information is captured from hospital Medicare claims data.

The CMS Hospital Compare Web site will show whether a hospital's mortality or readmissions rate is "better than," "no different from," or "worse than" the U.S. national rate.

CMS said the Hospital Compare Web site is an important resource for consumers and it reports that in 2008 the site had over 18 million page views. This year, it has received about 1 million page views per month.

The CMS mortality and the readmissions measures have been endorsed by the National Quality Forum and are supported by the Hospital Quality Alliance. CMS officials said the ratings are used to inform hospitals and help them improve care.

According to CMS, Hospital Compare data show that for patients admitted to a hospital for heart attack treatment, 19.9 percent of them will return to the hospital within 30 days, 24.5 percent of patients admitted for heart failure will return to the hospital within 30 days, and 18.2 percent of patients admitted for pneumonia will return to the hospital within 30 days.

"Providing readmission rates by hospital will give consumers even better information with which to compare local providers," said Charlene Frizzera, CMS acting administrator. "Readmission rates will help consumers identify those providers in the community who are furnishing high-value healthcare with the best results."

According to Department of Health and Human Services Secretary Kathleen Sebelius, the Obama administration and Congress have both named the reduction of readmissions as a target area for health reform. "When we reduce readmissions, we improve the quality of care patients receive and cut health care costs," she said.

CMS has been tracking the outcomes of hospital care since 2007 when Hospital Compare debuted 30-day mortality rates for heart attack and heart failure. This is the first year that CMS will use three years' of data to calculate rates on hospitals.

"Using three years of data for our mortality measures is a critical development in our effort to inform the public about hospital quality," said Barry M. Straube, MD, CMS chief medical officer and director of the Agency's Office of Clinical Standards and Quality. "More data gives a clearer picture of the quality of care delivered at different hospitals over time, which ultimately increases the value of our mortality information to hospital patients, health care payers, employers, policymakers, and other health care stakeholders."